Figure 2

Dnmt1s protein expression during preimplantation development. A. Relative amount of Dnmt1s protein in fully grown wild-type MII oocytes, and in embryos at different stages of development. MII = MII oocytes; 1 = 1-cell; 2 = 2-cell; 4 = 4-cell; 8 = 8-cell; Bl = blastocyst. Sample sizes: 105 wild-type MII oocytes; 105 1-cell embryos; 110 2-cell embryos; 110 4-cell embryos; 110 8-cell embryos; 120 blastocysts. B. Relative stability of oocyte-derived Dnmt1o and Dnmt1s proteins from homozygous Dnmt1^1s/1omice during preimplantation development to the 8-cell stage. Sample sizes: 22 MII oocytes; 21 8-cell embryos. The blot was first probed with UPT82, stripped and then reprobed with UPTC21. The assay was repeated, and nearly identical results were obtained (data not shown). C. Relative levels of maintenance methyltransferase activity (MA) per oocyte. MA is expressed as [³H]methyl group incorporation into the synthetic template poly(dIdC). Oocyte genotype is the genotype of the diploid precursor of the analyzed MII oocyte. The assay was performed on three separate occasions (1–3). The background measurement is the cpm in sample containing poly(dIdC) and S-adenosyl methionine, but no oocyte extract. Dnmt1o MA/Total MA was calculated as [(Dnmt1^+/+ – background) – (Dnmt1^Δ1o/Δ1o– background)]/(Dnmt1^+/+ – background), expressed as a percentage.